1. Field of the Invention
The invention disclosed herein relates to a diverter apparatus and system for redirecting the flow of drilling fluid or mud and cuttings that would otherwise be blown upward to the rig floor during a "kick" encountered during initial hole drilling. In general, the apparatus and system according to the invention may be used beneath the drilling floor of any land or marine drilling rig, but in particular the invention finds application with floating drilling equipment. More particularly, the invention relates to a vent line system for connecting to a diverter in which the system has a blast deflecting means to deflect the mud and cuttings flowing in the vent line overboard assuring that no means are provided to prevent such flow.
2. Description of the Prior Art
When drilling an oil or gas well from a floating vessel, an initial large diameter bore hole is established to shallow depths. Protective conduit typically thirty (30) inches in diameter, is secured in the shallow bore through which the drilling takes place. Then a subsea riser is put in place extending from the sea floor to the drilling rig platform.
Flow diverters are typically provided below the rig floor and between the riser and the rotary table of the drilling rig for the purpose of safety venting unbalanced well bore pressure which may produce an upward flow of well flow fluid in the riser having sufficient impetus to issue from the top of the riser, thereby contributing a hazard to personnel and equipment. Such an occurrence, called a "kick" results when the formation fluid pressure exceeds the head in the riser and borehole and is sometimes encountered in conductor hole drilling, making a flow diverter essential before blowout preventers are connected to the drilling system. A flow diverter is considered necessary for safe operation on a floating offshore drilling rig where blowout preventers are placed on the sea floor only after the casing has been set to a considerable depth below the sea floor.
Flow diverter systems which have been provided in the past have faced significant safety problems because the available equipment has required that valves external to the diverter be placed in the vent line system. Such valves have been necessary because the vent line was in general open to the annulus of the drilling conduit below the diverter element adapted for closing the vertical flow path of the bore. The vent line valve was opened simultaneously with or prior to the closing of the diverter element. Typically a "T" joint has been provided to direct flow in the vent line to one of two discharge lines, one leading to the port side of the vessel, the other to the starboard. Valves in each of the discharge lines enabled rig personnel to close one of the discharge lines so that vent line flow could be discharged to the leeward side of the vessel.
In the past, such external valves have sometimes been locked closed by rig personnel while testing the flow diverter system, but after the diverter had been made operational during drilling, the external valves have been unintentionally left locked closed. On other occasions, control system elements for remotely operating the external valves have been inadvertently incorrectly connected, resulting in simultaneous closure of all of the external diverter system valves and the diverter itself. If such flow diverters have closed about the annulus of a drill pipe or other object in the well bore, such flow diverter systems have created an extremely dangerous situation, and in fact, in some cases they have exploded with the result of loss of life and property. The complexity of the circuitry that sequences the operation of the valves and the diverter invites mistakes in connection even by skilled technicians.
It is an object of the invention described below, to provide a vent line system which, when used in combination with a novel flow diverter which requires no external vent line valves, is failsafe; that is, when a kick occurs during shallow hole drilling of a well before a blowout preventer has been provided, that kick cannot be accidently confined by the vent line system to build pressure and explode, even if controls are misconnected or malfunctioning.
It is a further object of the invention to provide a blast deflecting system that always has an open vent path.
It is a still further object of the invention to provide a blast deflecting device which requires but a single motion to operate, is simple and relatively inexpensive to manufacture.